Stock Incentive and Purchase Plans (Tables)

12 Months Ended

Apr. 26, 2013

Stock Incentive and Purchase Plans [Abstract]

Allocation of Share-Based Compensation Costs by Expense Category

	52 Weeks Ended April 26, 2013		52 Weeks Ended April 27, 2012		52 Weeks Ended April 29, 2011
Cost of goods sold	$	504,715	$	578,157	$	452,106
Selling, general and administrative		7,949,517		8,106,663		4,784,081
Research and development		3,229,017		2,417,417		1,128,816
Total stock-based compensation expense	$	11,683,249	$	11,102,237	$	6,365,003
Income tax benefit related to awards recognized in the consolidated statements of income		3,810,136		3,461,453		1,992,308
Total expense, net of income tax benefit	$	7,873,113	$	7,640,784	$	4,372,695

Allocation of Share-Based Compensation Costs by Type of Arrangement

	52 Weeks Ended April 26, 2013		52 Weeks Ended April 27, 2012		52 Weeks Ended April 29, 2011
Service-based stock option awards	$	2,916,855	$	2,639,748	$	2,505,417
Service-based restricted and restricted stock unit awards		5,067,292		5,290,854		3,859,586
Performance-based restricted stock and restricted stock unit awards		3,699,102		3,171,635		0
Total stock-based compensation expense	$	11,683,249	$	11,102,237	$	6,365,003

Schedule of Stock-Based Compensation Cost Unrecognized

	April 26, 2013
		Unrecognized Compensation Cost	Weighted Average remaining Vesting Period (in years)
Service-based stock option awards	$	6,550,810	2.72
Service-based restricted and restricted stock unit awards		7,786,730	2.18
Performance-based restricted stock and restricted stock unit awards		3,866,162	1.46
Total stock-based compensation cost unrecognized	$	18,203,702

Schedule of Stock Option Valuation Assumptions

	52 Weeks Ended April 26, 2013	52 Weeks Ended April 27, 2012	52 Weeks Ended April 29, 2011
Dividend Yield (1)	0	0	0
Risk-free interest rate - based on grant date (2)	0.94% - 1.57%	0.73% - 2.23%	1.18% - 2.50%
Expected option term - in years per group of employees/consultants (3)	6.41 - 9.39	4.08 - 6.59	4.12 - 6.50
Expected volatility at grant date (4)	44.95% - 51.14%	47.04% - 59.07%	45.14% - 52.54%

Schedule of Stock Options Rollforward

	52 Weeks Ended April 26, 2013
Options	Number of Optioned Shares	Wtd. Avg. Exercise Price		Wtd. Avg. Remaining Contractual Term (years)	Aggregate Intrinsic Value(1)
Outstanding — beginning of year	1,441,057	$	23.75
Granted	238,459		43.63
Exercised	(501,050)		23.94
Forfeited	(15,772)		28.52
Expired	(1,267)		36.87
Outstanding — end of year	1,161,427		27.67	6.24	$	18,164,690
Fully vested and exercisable — end of year	577,403		23.40	4.22		11,433,687
Fully vested and expected to vest — end of year (2)	1,130,897		27.45	6.17		17,922,143

Summary of Stock Option Activity

	52 Weeks Ended April 26, 2013		52 Weeks Ended April 27, 2012		52 Weeks Ended April 29, 2011
Weighted average grant date fair value  of stock option awards during the fiscal year	$	20.55	$	12.31	$	11.78
Aggregate intrinsic value of stock option exercises during the fiscal year	$	11,475,610	$	5,636,206	$	9,632,100

Schedule of Restricted Stock Service-Based Activity Rollforward

	52 Weeks Ended April 26, 2013
	Number of Shares	Wtd. Avg. Grant Date Fair Value
Non-vested shares at the beginning of year	639,033	$	20.75
Granted	117,262		44.31
Vested	(381,532)		17.38
Forfeited	(7,029)		28.18
Non-vested shares at end of year	367,734	$	31.61

Summary of Restricted Stock Service-Based Activity

	52 Weeks Ended		52 Weeks Ended		52 Weeks Ended
	April 26,		April 27,		April 29,
	2013		2012		2011
Weighted average grant date fair value of service-based share grants issued during the fiscal year	$	44.31	$	26.58	$	27.23
Aggregate fair value of service-based share grants that vested during the year	$	15,969,922	$	7,638,546	$	2,978,345

Schedule of Performance-Based and Market-Based Restricted Stock and Restricted Stock Unit Award Activity Rollforward

	52 Weeks Ended April 26, 2013
	Number of Shares	Wtd. Avg. Grant Date Fair Value
Non-vested shares at the beginning of year	464,125	$	25.36
Granted	8,982		50.10
Vested	(76,946)		27.34
Forfeited	0		0
Non-vested shares at end of year	396,161	$	25.54

Summary of Performance-Based and Market-Based Restricted Stock and Restricted Stock Unit Activity

	52 Weeks Ended		52 Weeks Ended		52 Weeks Ended
	April 26,		April 27,		April 29,
	2013		2012		2011
Weighted average grant date fair value of performance-based share grants issued during the fiscal year	$	50.10	$	25.23	$	0
Aggregate fair value of performance-based share grants that vested during the year	$	3,318,681	$	0	$	0